Axially compact gear pump

ABSTRACT

The invention provides an axially compact gear pump comprising a housing ( 13 ) and end plate ( 14 ). Dowels ( 18 ) extend from the housing through the end plate to locate the end plate ( 14 ) relative to the housing ( 13 ), and project from the end plate ( 14 ) for locating the assembled gear pump ( 10 ) on its drive means in use. Assembly bolts ( 20 ) extend through the housing ( 13 ) and into the end plate ( 14 ) to hold the gear pump together for transportation prior to use, but mounting bolts ( 22 ) for mounting the gear pump on the drive means or on a test plate in use pass completely through both the housing ( 13 ) and end plate ( 14 ), providing enhanced rigidity to the assembly.

BACKGROUND OF THE INVENTION

[0001] The invention relates to gear pumps for mounting on a drive means in an axially compact manner.

[0002] Gear pumps are known for mounting on a drive means such as an engine block of an internal combustion engine or on a hydraulic piston pump which in turn is mounted on an internal combustion engine to create an integrated hydraulic package. Such pumps and pump assemblies are typically used in agricultural tractors or industrial vehicles which require a regular and reliable source of hydraulic fluid.

[0003] The design and mounting of conventional gear pumps is as follows. A housing and an end cap together define a gear pumping chamber housing a pair of meshing gears of the pump. The end cap is located on the housing by means of a pair of dowels straddling aligned blind bores in the housing and end cap, and is secured to the housing by four bolts passing through the housing and into the end cap. A pair of flanges extend from opposite sides of the end cap and each flange is apertured to receive a mounting bolt which is used to mount the gear pump either onto a test plate for testing purposes or onto the engine block or hydraulic piston pump for normal use. The flanged end cap is substantial in size and is robust so as to maintain the necessary alignment of the gear wheel axes with the bearings in the housing and with the drive shaft of the engine. The axial length of the end cap must in essence be sufficient to withstand the applied loadings in use while maintaining accurate alignment.

[0004] It is an object of the invention to reduce the axial length of the gear pump. Simply reducing the axial length of the flanged end cap is not an acceptable option because of the need to maintain rigidity in the face of substantial applied loadings.

BRIEF SUMMARY OF THE INVENTION

[0005] The invention provides an axially compact gear pump comprising a housing and an end plate defining therebetween a gear pumping chamber housing a pair of meshing gears of the pump wherein:

[0006] dowel means extend from the housing through the end plate to locate the end plate relative to the housing, and project from the end plate for locating the assembled and plate and housing relative to a drive means in use;

[0007] assembly bolts for holding together the end plate and housing prior to mounting the gear pump on a test plate or on the drive means extend through the housing and into the end plate; and

[0008] mounting bolts for mounting the gear pump on the test plate or the drive means extend through the housing and end plate and project from the end plate for connection to the test plate or drive means.

[0009] The end plate of the pump of the invention is not connected to the test plate or drive means by means of flanges as in the prior art pumps. The unique arrangement of dowels and bolts securing the end plate to the housing and the pump to the test plate or drive means is sufficient to maintain rigidity of the end plate both on test and in final use. The test plate or drive means contributes directly to the rigidity of the end plate and permits the design of a pump that utilizes an end plate which would not have sufficient structural rigidity if mounted by conventional flanges.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a perspective view of a known gear pump incorporating a flanged end cap;

[0011]FIG. 2 is an axial sectional through the flanged end cap of FIG. 1;

[0012]FIG. 3 is an end view of the gear pump of FIG. 1, taken from the mounting end (the left-hand side of FIGS. 1 and 2),

[0013]FIGS. 4a and 4 b are schematic side illustrations of a prior art gear pump (FIG. 4a) and a pump of the invention (FIG. 4b), both mounted on a closed circuit hydraulic piston pump and on a diesel engine to illustrate the axially shorter length of the assembly using a pump according to the invention;

[0014]FIG. 5 is a side elevation of the bellhousing flange/closed circuit hydraulic piston pump/gear pump subassembly of FIG. 4b;

[0015]FIG. 6 is an end view of the gear pump of FIG. 4b, taken from the mounting end (the left-hand side of FIG. 4b);

[0016]FIG. 7 is a staggered section taken along the line VII-VII of FIG. 6;

[0017]FIG. 8 is a side elevation of the pump of FIG. 6;

[0018]FIG. 9 is a plan view of the pump of FIG. 6 mounted on a test plate, and

[0019]FIG. 10 is an end view of the pump of FIG. 9, taken from the end remote from the test plate (the right-hand side of FIG. 9).

DETAILED DESCRIPTION OF THE INVENTION

[0020] Referring first to FIGS. 1 to 3, there is illustrated a conventional known gear pump, which comprises a housing 1 and an end cap 2 which together house meshing spur gears of the pump (not shown). The end cap 2 is positioned on the housing 1 by means of dowels (not shown) which are located in blind bores in the end cap and housing, straddling the junction between the end cap and housing. The blind bores in the end cap 2 are identified by reference numeral 3 in FIG. 2. The end cap 2 is made fast to the housing 1 by four assembly bolts 4 (FIG. 1) passing through the housing 1 and into the end cap 2.

[0021] Cast in one piece with the remainder of the end cap 2 are a pair of flanges 5 which are used to anchor the gear pump to the engine housing or axial piston pump on which it is to be mounted in use. Two mounting bolts 6 pass through bores in the flanges 5 to mount the gear pump on the engine housing or axial piston pump. FIG. 4a illustrates the total axial length of the assembly of engine axial piston pump and gear pump.

[0022]FIG. 4b illustrates how an axially more compact mounting is provided according to the invention. From FIG. 5 it will be seen that the gear pump 10 of the invention is attached to a closed circuit hydraulic piston pump 11 which in turn is mounted on the engine through a conventional bellhousing flange 12.

[0023] Referring to FIGS. 6 to 10, it will be seen that the pump 10 comprises a housing 13 and an end plate 14 which together define a gear pumping chamber for a pair of meshing gears 15, 16 (FIG. 7) of the pump. One of the gears, 16, is in the input gear and includes a splined drive shaft 17 which extends through the end plate 14 to take a drive input directly from a driven shaft of the engine block or closed circuit hydraulic piston pump 11.

[0024] Alignment between the housing 13, end plate 14 and hydraulic piston pump 11 is maintained by a pair of dowels 18 (see FIGS. 7 and 8). Each dowel 18 passes through a through bore in the end plate 14 and projects from both front and back faces of the end plate 14. On one side the projecting dowels engage in blind bores 19 of the housing 13. On the other side the dowel 18 engage in blind bores (not shown) of the closed circuit hydraulic piston pump 11. A pair of assembly bolts 20 (FIG. 10) pass through the housing 13 into screw-threaded engagement with the end plate 14 to hold the housing 13 and end plate 14 together prior to mounting on an engine block or on the closed circuit hydraulic piston pump 11. The actual mounting of the gear pump 10 onto a test plate 21 (FIG. 10) or onto the closed circuit hydraulic piston pump 11 or onto an engine block is achieved by means of four heavy duty mounting bolts 22 (FIG. 10) which pass through pairs of aligned bores in the housing 13 and end plate 14. One such pair of aligned bores 23 is shown in FIG. 8 in broken lines.

[0025] Because the mounting bolts 22 serve to augment the clamping together of the housing 13 and end plate 14. The assembled gear pump has very high rigidity when mounted either on the test plate 21 (FIG. 10) or on an engine or piston pump (FIG. 4b). The end plate 14 can therefore be made much less substantial than was necessary in a conventional prior art pump of FIGS. 1 to 3, and the axial length of the gear pump can be reduced accordingly. 

What is claimed is:
 1. An axially compact gear pump comprising a housing and end plate defining therebetween a gear pumping chamber housing a pair of meshing gears of the pump wherein: dowel means extend from the housing through the end plate to locate the end plate relative to the housing, and project from the end plate for locating the assembled end plate and housing relative to a drive means in use; assembly bolts for holding together the end plate and housing prior to mounting the gear pump on a test plate or on the drive means extend through the housing and into the end plate; and mounting bolts for mounting the gear pump on the test plate or the drive means extend through the housing and end plate and project from the end plate for connection to the test plate or drive means.
 2. A gear pump according to claim 1, wherein the dowel means are two in number.
 3. A gear pump according to claim 2, wherein the assembly bolts are two in number.
 4. A gear pump according to claim 3, wherein the dowel means and assembly bolts are arranged at the corners of an imaginary rectangle having the dowel means at opposite corners and the assembly bolts at opposite corners. 